Wireless communication method using trigger information, and wireless communication terminal using same

ABSTRACT

Provided is a wireless communication terminal that communicates wirelessly. The wireless communication terminal includes: a transceiver; and a processor. The processor receiving trigger information from a base wireless communication terminal using the transceiver, and transmits an Aggregate-MAC Protocol Data Unit (A-MPDU) to the base wireless communication terminal based on the trigger information.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal using trigger information.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11 ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel Therefore, required is a technology capable of efficiently usingbandwidths by simultaneously transmitting data between a plurality ofterminals and base terminals.

DISCLOSURE Technical Problem

An object of an embodiment of the present invention is to provide awireless communication terminal using trigger information.

Technical Solution

According to an embodiment of the present invention a wirelesscommunication terminal communicating wirelessly includes: a transceiver;and a processor, wherein the processor is configured to receive triggerinformation from a base wireless communication terminal using thetransceiver, and transmit an Aggregate-MAC Protocol Data Unit (A-MPDU)to the base wireless communication terminal based on the triggerinformation.

The processor may be configured to determine whether to aggregate anMPDU requesting an immediate response to generate the A-MPDU based onthe trigger information.

The trigger information may be a trigger frame and the trigger frame mayinclude a signaling field indicating whether the wireless communicationterminal is allowed to aggregate an MPDU requesting an immediateresponse and generate the A-MPDU. The processor may be configured toaggregate an MPDU requesting an immediate response to generate theA-MPDU based on the signaling field.

When the value of the signaling field is a predetermined value, theprocessor may be configured to generate the A-MPDU that does not includean MPDU requesting an immediate response. When the value of thesignaling field is within a predetermined range, the signaling field mayindicate the maximum number of TIDs that the A-MPDU is capable of havingwhen the wireless terminal generates the A-MPDU, and the processor maybe configured to generate the A-MPDU according to the maximum number ofTIDs.

In addition, when the value of the signaling field is within apredetermined range, the processor may be configured to aggregate theaction frame regardless of the maximum number of TIDs that the A-MPDU iscapable of having to generate the A-MPDU.

The MPDU not requesting the immediate response may include a Quality ofService (QoS) Null frame not requesting an ACK for data transmission.

In addition, the MPDU not requesting the immediate response may includean Action No Ack frame not requesting an ACK for data transmission.

In addition, the MPDU requesting the immediate response may include anaction frame.

At this time, when the value of the signaling field is within apredetermined range, the processor may be configured to aggregate theaction frame regardless of the maximum number of TIDs that the A-MPDU iscapable of having to generate the A-MPDU.

The MPDU not requesting the immediate response may include an Action NoAck frame not requesting an ACK for data transmission.

When the trigger information is included in the MAC header, theprocessor may be configured to aggregate any one of an ACK frame and aBlock ACK (BA) frame, and an MPDU not requesting an immediate responsewithout the MPDU requesting the immediate response to generate theA-MPDU.

The MPDU not requesting the immediate response may include at least oneof a QoS Null frame not requesting an ACK for data transmission and anAction No Ack frame not requesting an ACK for data transmission.

According to an embodiment of the present invention, a base wirelesscommunication terminal communicating wirelessly includes; a transceiver;and a processor, wherein the processor is configured to transmit triggerinformation to a plurality of wireless communication terminals using thetransceiver, and receive an Aggregate-MAC Protocol Data Unit (A-MPDU)generated based on the trigger information from at least one of theplurality of wireless communication terminals.

The trigger information may be a trigger frame, and the trigger framemay include a first signaling field indicating information on a type ofMPDU included in the A-MPDU, wherein when a wireless communicationterminal corresponding to the first signaling field is not allowed toaggregate an MPDU requesting an immediate response and generate theA-MPDU, the processor may be configured to set the value of the firstsignaling field to a predetermined value.

When a wireless communication terminal corresponding to the firstsignaling field is allowed to aggregate an MPDU requesting an immediateresponse and generate the A-MPDU, the processor may be configured to setthe value of the first signaling field according to the maximum numberof TIDs that the A-MPDU is capable of having.

The maximum number of TIDs that the A-MPDU is capable of having mayindicate the maximum number of TIDs requesting an immediate responsethat the A-MPDU is capable of having.

A Quality of Service (QoS) null frame not requesting an ACK for datatransmission may not correspond to a TID requesting an immediateresponse.

The trigger frame may include a second signaling field indicatingwhether channel sensing is required when transmitting the trigger-basedPhysical Layer Data Unit (PPDU).

The processor may be configured to set the value of the first signalingfield based on the value of the second signaling field.

When the second signaling field is set to indicate that channel sensingfor the trigger-based PPDU transmission is not required, the processormay be configured to set the value of the first signaling field to thepredetermined value.

The trigger frame may include a third signaling field indicatinginformation on a length of the trigger-based PPDU, wherein the processormay be configured to set the value of the first signaling field based onthe value of the third signaling field.

According to an embodiment of the present invention, an operation methoda wireless communication terminal communicating wirelessly includesreceiving trigger information from a base wireless communicationterminal; and transmitting an Aggregate-MAC Protocol Data Unit (A-MPDU)to the base wireless communication terminal based on the triggerinformation.

Advantageous Effects

An embodiment of the present invention provides a wireless communicationmethod using trigger information and a wireless communication terminalusing the same.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless LAN system according to an embodiment of thepresent invention.

FIG. 2 shows a wireless LAN system according to another embodiment ofthe present invention.

FIG. 3 shows a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 shows a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 shows a process that a station sets an access point and a linkaccording to an embodiment of the present invention.

FIG. 6 shows a method of generating an Aggregate-MAC Protocol Data Unit(A-MPDU) by a wireless communication terminal according to an embodimentof the present invention.

FIG. 7 shows a method for transmitting a Block Ack (BA) frame for anA-MPDU by a wireless communication terminal according to an embodimentof the present invention.

FIG. 8 illustrates an operation of a wireless communication terminalaccording to an embodiment of the present invention to transmit anA-MPDU based on maximum number of TIDs information.

FIG. 9 shows an operation of a wireless communication terminal accordingto another embodiment of the present invention to transmit an A-MPDUbased on maximum number of TIDs information.

FIG. 10 shows an operation of a wireless communication terminalaccording to another embodiment of the present invention to transmit anA-MPDU based on maximum number of TIDs information.

FIG. 11 shows an operation of a wireless communication terminalaccording to another embodiment of the present invention to transmit anA-MPDU based on maximum number of TIDs information.

FIG. 12 shows an operation of the wireless communication terminalaccording to an embodiment of the present invention to set maximumnumber of TIDs information of a trigger frame.

FIG. 13 describes an operation in which a wireless communicationterminal according to an embodiment of the present invention transmitsan A-MPDU based on UL MU RS.

FIG. 14 describes an operation in which a wireless communicationterminal according to another embodiment of the present inventiontransmits an A-MPDU based on UL MU RS.

FIG. 15 describes an operation in which a wireless communicationterminal according to another embodiment of the present inventiontransmits an A-MPDU based on UL MU RS.

FIG. 16 shows that an AP according to an embodiment of the presentinvention signals the transmission power of a trigger frame to aplurality of wireless communication terminals using a trigger frame, anda plurality of wireless communication terminals adjust the transmissionpower of an MU PPDU based on the transmission power of a trigger frame.

FIG. 17 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to an embodiment of the presentinvention.

FIG. 18 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 19 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 20 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 21 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 22 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 23 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

FIG. 24 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2016-0085764 (2016 Jul. 6), Nos. 10-2016-0117898(2016 Sep. 13), and Nos. 10-2016-0048145 (2017 Apr. 13) filed in theKorean Intellectual Property Office and the embodiments and mentioneditems described in the respective applications are included in theDetailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STAS, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

In a specific embodiment, the AP 200 may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in an independent network, such as an ad-hoc network, whichis not connected to an external distribution service. In addition, theAP 200 may be at least one of a base station, an eNB, and a transmissionpoint TP. The AP 200 may also be referred to as a base wirelesscommunication terminal.

An wireless communication terminal according to an embodiment of thepresent invention may use a data unit which is a data processing unitfor a each layer to transmit and receive data. Specifically, thewireless communication terminal may generate a MAC Protocol Data Unit(MPDU) in a medium access control (MAC) layer and a physical protocoldata unit (PPDU) in a physical layer. In addition, the wirelesscommunication terminal receiving the data may receive the PPDU andobtain the MPDU from the PPDU. Through this operation, the wirelesscommunication terminal may increase the reliability and efficiency ofdata transmission. For convenience of explanation, a wirelesscommunication terminal that transmits data is referred to as anoriginator, and a wireless communication terminal that receives data isreferred to as a recipient. The originator may aggregate a plurality ofMPDUs to generate an Aggregate-MAC Protocol Data Unit (A-MPDU) includingthe plurality of MPDUs. The originator may transmit the generated A-MPDUto the recipient. A specific operation of the wireless communicationterminal related to the A-MPDU will be described with reference to FIGS.6 to 24.

FIG. 6 shows a method of generating an Aggregate-MAC Protocol Data Unit(A-MPDU) by a wireless communication terminal according to an embodimentof the present invention.

The wireless communication terminal may generate the A-MPDU as describedabove and transmit the A-MPDU to the recipient. Specifically, thewireless communication terminal may insert a plurality of MPDUs havingthe same TID to generate an A-MPDU. Through this, the wirelesscommunication terminal may increase the transmission efficiency.Specifically, the wireless communication terminal may increase thetransmission efficiency by reducing the number of channel accesscompetition procedures required for data transmission. The wirelesscommunication terminal may insert a delimiter indicating information onthe MPDU and insert one or a plurality of MPDUs to generate an A-MPDU.The A-MPDU may be divided into Pre-EOF padding and EOF padding. At thistime, the delimiter may include an EOF field indicating the end of thePre-EOF padding portion included in the A-MPDU. Also, the EOF field mayindicate that the MPDU corresponding to the delimiter requests an ACKthat does not include the BA bitmap. Also, the delimiter may include anMPDU Length field indicating the length of the MPDU. Also, the delimitermay include a CRC field indicating a CRC value for error detection ofthe delimiter. In addition, the delimiter may include a DelimiterSignature field indicating a pattern for detecting the delimiter. Thewireless communication terminal inserts a delimiter in which a value ofthe EOF field is 0 and a value of the MPDU Length field is non-zero intothe A-MPDU and inserts the MPDU after the delimiter. The wirelesscommunication terminal may insert one or a plurality of MPDUs and aplurality of delimiters indicating information on each of one or aplurality of MPDUs into the A-MPDU to generate Pre EOF Padding A-MPDU.At this time, the inserted MPDU may be a data MPDU corresponding to aTID agreed with BlockACK. The wireless communication terminal may insertEOF Padding after the Pre EOF Padding A-MPDU. At this time, the EOFpadding may indicate one or a plurality of delimiters in which the valueof the EOF field is 1 and the value of the MPDU Length field is 0. Whenthe recipient detects a delimiter in which the value of the EOF field is1 and the value of the MPDU Length field is 0, the recipient maydetermine that the A-MPDU transmission ends.

When the wireless communication terminal transmits a large amount ofdata, the wireless communication terminal may increase the transmissionefficiency by using the A-MPDU. However, the recipient receiving theA-MPDU is required to transmit a Block ACK (BA) frame including the BAbitmap in response to the A-MPDU. Therefore, it may be inefficient forthe wireless communication terminal to transmit one MPDU using theA-MPDU. Therefore, a recipient receiving a single-MPDU (S-MPDU) that isan A-MPDU including one MPDU may transmit an ACK frame instead of a BAframe to the originator in response to the A-MPDU. Specifically,regardless of the BA agreement for one MPDU, the recipient may transmitan ACK frame instead of a BA frame to the originator in response to theA-MPDU. In addition, the originator may set the value of the EOF fieldto 1 and the value of the MPDU Length field to a non-zero value in thedelimiter located before the MPDU. Also, when the value of the EOF fieldof the delimiter included in the A-MPDU received by the recipient is 1and the value of the MPDU Length field is 0, the recipient may determinethat the received A-MPDU is the S-MPDU. In addition, the originator mayinsert EOF padding after the MPDU in the S-MPDU.

In the embodiment of FIG. 6(a), the wireless communication terminalaggregates a plurality of MPDUs with a TID of 2 and a plurality ofdelimiters (Pre EOF Padding) indicating information on each of theplurality of MPDUs to generate an A-MPDU. At this time, the MPDU islocated after the delimiter indicating the information of thecorresponding MPDU. In addition, the wireless communication terminalinserts EOF padding. In the embodiment of FIG. 6(b), the wirelesscommunication terminal aggregates one MPDU with a TID of 2 and adelimiter (Pre EOF Padding) indicating information on a correspondingMPDU to generate an S-MPDU. At this time, the value of the EOF field ofthe delimiter is 1, and the value of the MPDU Length field is not 0. Inaddition, the wireless communication terminal inserts EOF padding intothe S-MPDU. Referring to FIG. 7, an operation in which an originatortransmits an A-MPDU and a recipient transmits a response to an A-MPDUwill be described in detail.

FIG. 7 shows a method for transmitting a Block Ack (BA) frame for anA-MPDU by a wireless communication terminal according to an embodimentof the present invention.

As described above, the wireless communication terminal may generate anA-MPDU by combining only MPDUs having the same traffic identifier (TID).In another specific embodiment, the wireless communication terminal maycombine a plurality of MPDUs having different TIDs to generate oneA-MPDU. For convenience of explanation, an A-MPDU including a pluralityof MPDUs corresponding to a plurality of different TIDs is referred toas a Multi-TID A-MPDU or an A-MPDU with Multiple TIDs. Through this, thewireless communication terminal may increase the transmission efficiencyof the A-MPDU. In addition, a wireless communication terminal maytransmit an A-MPDU with Multiple TIDs using a Physical Layer ProtocolData Unit (HE PPDU). At this time, the HE PPDU may be an HE Multi User(MU) PPDU. Also, the HE PPDU may be an HE trigger-based PPDU.

The wireless communication terminal may set parameters related to A-MPDUand BA frame transmission in a link setup procedure. The wirelesscommunication terminal may set parameters related to transmission of anA-MPDU with Multiple TIDs in the link setup procedure. Specifically, thewireless communication terminal may transmit the maximum number of TIDsinformation indicating the maximum number of TIDs that the wirelesscommunication terminal is capable of simultaneously receiving in thelink setup procedure. At this time, the wireless communication terminalmay transmit the maximum number of TIDs information using the HEcapability information element indicating the capability of theterminal. This is because as the number of TIDs of an A-MPDU withMultiple TIDs increases, the high processing capability of the wirelesscommunication terminal receiving the A-MPDU may be required. The maximumnumber of TIDs information may be the maximum number of TID field of theHE capability information element. The maximum number of TIDsinformation transmitted by the AP to the non-AP wireless communicationterminal may indicate the maximum number of TIDs that the MPDU includedin the UpLink (UL) A-MPDU transmitted by the corresponding non-APwireless communication terminal is capable of having. In addition, themaximum number of TIDs information transmitted by the non-AP wirelesscommunication terminal to the AP may indicate the maximum number of TIDsthat the DownLink (DL) A-MPDU transmitted by the corresponding AP iscapable of having. In the link setup procedure, the wirelesscommunication terminal may transmit the maximum number of TIDsinformation using the management frame. At this time, the managementframe may be at least one of a probe request frame, a probe responseframe, an authentication request frame, an authentication responseframe, an association request frame, an association response frame, anda beacon frame. Also, when the AP transmits the maximum number of TIDsinformation using the beacon frame, the maximum number of TIDsinformation may indicate the number of TIDs that the AP is capable ofsimultaneously receiving. Specifically, when an AP transmits the maximumnumber of TIDs information using a beacon frame, the maximum number ofTIDs information may indicate the maximum number of TIDs that is allowedto be transmitted in the MU UL transmission, not the maximum number ofTIDs that the MPDU included in the A-MPDU transmitted from any onewireless communication terminal to the AP is capable of having. This isbecause the AP transmits the beacon frame to the entire wirelesscommunication terminal of the BSS operated by the AP. In anotherspecific embodiment, the maximum number of TIDs information of thebeacon frame may be used for other purposes. In another specificembodiment, the maximum number of TID field of the beacon frame may be areserved field.

In the link setup procedure, the wireless communication terminal mayreceive All ACK from the recipient and transmit an All ACK capableindicator indicating whether the wireless communication terminal iscapable of processing the All ACK. At this time, the All ACK is an ACKindicating that the recipient receives all the MPDUs included in anA-MPDU transmitted by one originator or the Multiple TID A-MPDUstransmitted by one originator. When an All ACK is transmitted, theoriginator may not know the information on the fragment transmitted fromthe All ACK. To process the All ACK, the originator must storeinformation on the fragments transmitted by the originator. This isbecause the originator may not be able to store information on fragmentstransmitted by the originator according to the capability. Specifically,the wireless communication terminal may transmit an All ACK capableindicator indicating whether the All ACK can be processed using the HEcapability information element.

The wireless communication terminal may fragment and transmit at leastone of a MAC service data unit (MSDU), an Aggregate (A)-MSDU, and amanagement protocol data unit (MMPDU). For convenience of explanation, aportion of an MSDU, a portion of an A-MSDU, or a portion of an MMPDU,which are generated through fragmentation, is referred to as a fragment.In addition, a wireless communication terminal that transmits data isreferred to as an originator, and a wireless communication terminal thatreceives data is referred to as a recipient.

Specifically, the wireless communication terminal may generate aplurality of fragments by fragmenting at least one of an MSDU, anA-MSDU, and an MMPDU. At this time, the wireless communication terminalmay transmit the generated plurality of fragments to a plurality ofMPDUs. In addition, the wireless communication terminal receiving aplurality of fragments may defragment a plurality of fragments to obtainat least one of one MSDU, one A-MSDU, and one MMPDU. At this time, theMPDU may be an S-MPDU or an A-MPDU.

The recipient needs sufficient buffer capacity and processing capacityto defragment multiple fragments. Specifically, the recipient isrequired to store all fragments until the recipient receives all thefragments of the MSDU corresponding to the same sequence number. Thus,when the recipient supports the capability to receive fragments, theoriginator may transmit the fragments to the recipient. Eventually, theoriginator is required to know the fragmentation level that therecipient supports. The wireless communication terminal may signal onthe fragmentation level. Specifically, the wireless communicationterminal transmits information on the fragmentation level of thefragments that the wireless communication terminal may receive in thelink setup procedure with the AP, and receives information on thefragmentation level of the fragments that the AP may receive.Specifically, the wireless communication terminal may transmitinformation on the fragmentation level using the HE Capabilityinformation element. At this time, the HE Capability information elementmay indicate the capability of the wireless communication terminal.Further, the wireless communication terminal may transmit information onthe fragmentation level using at least one of a probe request frame, aprobe response frame, an authentication request frame, an authenticationresponse frame, an association request frame, and an associationresponse frame.

As described above, the HE capability information element may include aMax number of TID field, an All ACK capable indicator, and information(Fragmentation support level) indicating a fragmentation level supportedby the wireless communication terminal.

Further, the wireless communication terminal may set BA parameters inthe Add Block ACK (ADDBA) procedure. At this time, the BA parameter is aparameter used for BA frame transmission and BA frame reception. Thewireless communication terminal may request an ACK in the form of a BAframe using an ADDBA request frame. Also, the wireless communicationterminal may transmit a response to the ADDBA request frame using theADDBA response frame. The ADDBA request frame and the ADDBA responseframe may include a Block Ack Parameter Set element. At this time, theBlock Ack Parameter Set element includes information on the BAparameter. In addition, the wireless communication terminal may set BAparameters for each TID. Specifically, the wireless communicationterminal may negotiate the BA parameter setting for each TID. In aspecific embodiment, the wireless communication terminal may specify aTID that is the subject of the BA parameter setting negotiation usingthe TID field included in the Block Ack Parameter Set element. Theoriginator may request the BA parameter setting by transmitting an ADDBArequest frame. The recipient may receive the ADDBA request frame andtransmit the ADDBA response frame for the ADDBA request frame todetermine the BA parameter setting. When the originator receives anADDBA response frame and transmits an ACK frame for an ADDBA responseframe, the originator and recipient may set the BA parameters.

The wireless communication terminal may transmit buffer size informationindicating the number of MPDUs that may be stored until transmitting theBA frame after receiving the data in the ADDBA procedure. Specifically,the wireless communication terminal may transmit the buffer sizeinformation using the Block Ack Parameter Set element in the ADDBAprocedure. The wireless communication terminal may set the length of theBA bitmap based on a range of values that the buffer size information iscapable of having. Specifically, when the range of the value that thebuffer size information is capable of having is between 1 and X, thewireless communication terminal may set the length of the BA bitmap to Xbits. At this time, when the wireless communication terminal fails toreceive information on the length of the BA bitmap, the wirelesscommunication terminal may set the length of the BA bitmap to X bits.

When the AP performs DL transmission to the wireless communicationterminal, the AP may transmit the A-MPDU based on the capability of thewireless communication terminal signaled in the link setup procedure andthe BA parameter set in the ADDBA procedure. At this time, the wirelesscommunication terminal may transmit a BA frame or a Multi-STA Block ACK(M-BA) frame to the AP based on the capability of the AP and the BAparameter set in the ADDBA procedure.

When the AP simultaneously receives A-MPDUs from a plurality of wirelesscommunication terminals, it may be difficult to store a plurality ofMPDUs received by the AP in a buffer and maintain a score board. At thistime, the score board indicates information on the reception status ofeach of the MPDUs recorded by the AP. Therefore, the AP may use thetrigger frame to indicate the maximum number of TIDs that each wirelesscommunication terminal may have for the A-MPDU to transmit.Specifically, the AP may use the User Info field of the trigger frame toindicate the maximum TID to be transmitted by the wireless communicationterminal corresponding to the User Info field. At this time, thewireless communication terminal receiving the trigger frame may set thenumber of TIDs that the A-MPDU is capable of having based on the triggerframe. Specifically, the wireless communication terminal receiving thetrigger frame may set the number of TIDs of the MPDU included in theA-MPDU to transmit based on the maximum number of TIDs indicated by thetrigger frame, and transmit the A-MPDU to the AP. For example, thewireless communication terminal receiving the trigger frame may set thenumber of TIDs of the MPDU included in the A-MPDU to transmit, whichdoes not exceed the maximum number of TIDs indicated by the triggerframe, and transmit the A-MPDU to the AP.

Also, the wireless communication terminal may transmit an A-MPDU withMultiple TIDs in the SU transmission. Specifically, when the wirelesscommunication terminal uses the HE MU PPDU in the Single User (SU)Uplink (UL) transmission, it may be restricted that the wirelesscommunication terminal transmits the A-MPDU with Multiple TIDs. Thewireless communication terminal may use a relatively wide transmissionrange in a narrow frequency band using the HE MU PPDU in SU ULtransmission. At this time, when the wireless communication terminal isallowed to transmit the A-MPDU including the A-MPDU with multiple TIDs,a fairness problem may occur in terms of competition with other wirelesscommunication terminals. Therefore, when the wireless communicationterminal uses the HE MU PPDU in the SU UL transmission, it may berestricted that the wireless communication terminal transmits the A-MPDUwith Multiple TIDs. Through FIGS. 8 to 15, a specific operation of anoriginator and a recipient related to a Multi-TID A-MPDU will bedescribed.

As described above, when the recipient receives data with BA agreement,the recipient may maintain a score board that records the received databy each TID and AID. When a recipient receives a BAR frame requestingtransmission of a BA frame, the recipient must transmit a BA frame basedon the data reception record of the score board within a predeterminedtime. At this point, the predetermined time may be an SIFS. Therecipient may implement the score board in one-chip memory form forefficient processing. In addition, the recipient may record a record fora plurality of BA sessions on one score board. Therefore, when the APsimultaneously receives A-MPDUs from a plurality of wirelesscommunication terminals, it is difficult for the AP to maintain thescore board as the number of the plurality of wireless communicationterminals increases. Therefore, the AP may limit the number of TIDs ofthe MPDUs transmitted by the wireless communication terminalsparticipating in the UL MU transmission.

The AP may use the trigger information to indicate the maximum number ofTIDs that each wireless communication terminal is capable of having forthe A-MPDU to transmit. At this time, the trigger information may be atleast one of the UL MU response scheduling (UL MU RS) informationincluded in the trigger frame and the MAC header. Through FIGS. 8 to 12,an operation of the AP to indicate the maximum number of TIDs that theA-MPDUs to be transmitted by each wireless communication terminal usingthe trigger frame may have will be described.

FIG. 8 shows an operation of a wireless communication terminal accordingto an embodiment of the present invention to transmit an A-MPDU based onthe maximum number of TIDs information.

The AP may use the trigger frame to indicate information on the type ofan MPDU included in the A-MPDU to be transmitted to the AP by thewireless communication terminal. As described above, the AP may use thetrigger frame to indicate the maximum number of TIDs that the A-MPDUthat the wireless communication terminal transmits to the AP is capableof having. Specifically, the AP may use the User Info field of thetrigger frame to indicate the maximum TID to be transmitted by thewireless communication terminal corresponding to the User Info field. Ina specific embodiment, the AP may use the TID Aggregation Limit of theUser Info field of the trigger frame to indicate the maximum TID to betransmitted by the wireless communication terminal corresponding to theUser Info field. At this time, the wireless communication terminalreceiving the trigger frame may set the number of TIDs that the A-MPDUis capable of having based on the trigger frame. Specifically, thewireless communication terminal receiving the trigger frame may set thenumber of TIDs of the MPDU included in the A-MPDU to transmit based onthe maximum number of TIDs indicated by the trigger frame, and transmitthe A-MPDU to the AP. For example, the wireless communication terminalreceiving the trigger frame may set the number of TIDs of the MPDUincluded in the A-MPDU to transmit, which does not exceed the maximumnumber of TIDs indicated by the trigger frame, and transmit the A-MPDUto the AP. Through this, the AP may efficiently manage the scoreboard.In addition, BA bitmap lengths for each of a plurality of wirelesscommunication terminals may be adjusted.

In a specific embodiment, the value of the TID Aggregation Limit fieldmay indicate the maximum number of TIDs that the A-MPDU that thewireless communication terminal receiving the trigger frame transmits tothe AP is capable of having. For example, when the TID Aggregation Limitfield is a 3-bit field and has a value from 0 to 7, each of the values 0to 7 may indicate that the maximum number of TIDs of the A-MPDU to betransmitted to the AP corresponds to any one of 1 to 8.

In another specific embodiment, the AP may use the trigger frame toindicate that the wireless communication terminal indicated in thetrigger frame is not allowed to generate the A-MPDU to be transmitted tothe AP by aggregating the MPDU having the TID. Specifically, the AP mayset the TID Aggregation Limit to 0 to indicate that the wirelesscommunication terminal indicated in the trigger frame is not allowed togenerate the A-MPDU to be transmitted to the AP by aggregating the MPDUhaving the TID. However, when the A-MPDU includes an MPDU requesting animmediate response even when the MPDU does not have a TID, the size ofthe BA frame transmitted by the recipient in response to the A-MPDU maybe increased. Also, the burden of managing the scoreboard of therecipient may be increased. At this time, an immediate response mayindicate that the recipient transmits a response to the originatorwithin a predetermined time period in the same Transmission Opportunity(TXOP). Specifically, the predetermined period may be a ShortInter-Frame Space (SIFS).

In another specific embodiment, the AP may use the trigger frame toindicate that the wireless communication terminal indicated by thetrigger frame is not allowed to generate the A-MPDU to be transmitted tothe AP by aggregating the MPDUs that request an immediate response. Atthis time, the MPDU requesting an immediate response may include an MPDUincluding Quality of Service (QoS) data having a TID. In addition, anMPDU requesting an immediate response may include a Management MPDU(MMPDU) requesting an immediate response. Specifically, an MPDUrequesting an immediate response may include an action frame. The APsets the value of the TID Aggregation Limit field of the User Info fieldof the trigger frame to 0 to indicate that the wireless communicationterminal corresponding to the User Info field is not allowed to generatethe A-MPDU to be transmitted to the AP by aggregating MPDUs that requestan immediate response. When the TID Aggregation Limit field valueindicates a value other than 0, it may indicate the maximum number ofTIDs that the A-MPDU to be transmitted by the wireless communicationterminal indicated by the trigger frame to the AP may have. Also, whenthe trigger frame indicates that the wireless communication terminal isnot allowed to generate an A-MPDU to be transmitted to the AP byaggregating MPDUs that request an immediate response, the wirelesscommunication terminal may generate an A-MPDU to be transmitted to theAP by aggregating MPDUs not requesting an immediate response.Specifically, when the TID Aggregation Limit field value of the UserInfo field corresponding to the wireless communication terminal of thetrigger frame is 0, the wireless communication terminal may generate anA-MPDU to be transmitted to the AP by aggregating MPDUs not requestingan immediate response. In a specific embodiment, an MPDU not requestingan immediate response may include an MPDU including QoS data with theACK Policy set to No Ack. When the ACK Policy is set to No Ack, the ACKPolicy may represent that no ACK is requested for the correspondingframe. In addition, an MPDU not requesting an immediate response mayinclude a QoS null frame. At this time, the QoS Null frame may be a QoSNull frame in which ACK Policy is set to No Ack. In addition, an MPDUnot requesting an immediate response may include an action No Ack frame.

In another specific embodiment, the AP may use the trigger frame toindicate that the wireless communication terminal indicated by thetrigger frame is allowed to aggregate MPDUs without the number of TIDslimitation to generate an A-MPDU, and transmit the generated A-MPDU tothe AP. Specifically, the AP sets the value of the TID Aggregation Limitfield of the User Info field of the trigger frame to 7 to indicate thatthe wireless communication terminal corresponding to the User Info Fieldis allowed to aggregate MPDUs without the number of TIDs limitation togenerate an A-MPDU, and transmit the generated A-MPDU to the AP.

In the embodiment of FIG. 8, the AP sets the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame to 3 to indicate that the maximumnumber of TIDs that the A-MPDU to be transmitted to the AP by the thirdstation STA3 is 3. The third station STA3 determines the number of TIDsof the A-MPDU to be transmitted to the AP based on the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame. Specifically, the third station STA3determines the number of TIDs of the A-MPDU to be transmitted to the APas 3 based on the value of the TID Aggregation Limit field of the UserInfo field corresponding to the third station of the trigger frame. Thethird station STA1 aggregates an MPDU having a TID of 1, an MPDU havinga TID of 2, an MPDU having a TID of 3, an action frame, and a QoS nullframe to generate an A-MPDU to be transmitted to the AP. The thirdstation STA3 transmits the generated A-MPDU to the AP. The AP transmitsan M-BA frame to a plurality of wireless communication terminalsincluding the third station STA3 based on the A-MPDU received from thethird station SAT3. Through this embodiment, the AP adjusts the durationof the M-BA frame. In the embodiment of FIG. 8, the third station STA3treats MPDUs having no TID, such as a QoS Null frame and an actionframe, as being not included in the number of TIDs indicated by themaximum number of TIDs. However, when there is no BA agreement for aspecific TID, the response to the MPDU having the corresponding TID maynot affect the M-BA frame. Also, as described above, even an MPDU thatdoes not correspond to a specific TID may request an immediate response.Therefore, there is a need for a specific embodiment for comparing thenumber of TIDs and the maximum number of TIDs of the A-MPDU to betransmitted to the AP by the wireless communication terminal. This willbe described in detail with reference to FIGS. 9 to 12.

FIG. 9 shows an operation of a wireless communication terminal accordingto another embodiment of the present invention to transmit an A-MPDUbased on the maximum number of TIDs information.

The AP may use the trigger frame to indicate the maximum number of TIDswith the BA agreement that the A-MPDU to be transmitted by the wirelesscommunication terminal is capable of having. The wireless communicationterminal may calculate the number of TIDs of the A-MPDU based on thenumber of TIDs with the BA agreement. In the embodiments describedabove, when the wireless communication terminal compares the number ofTIDs of the A-MPDU to be transmitted to the AP and the maximum number ofTIDs, the wireless communication terminal may compare the number of TIDswith the BA agreement to the maximum number of TIDs. Specifically, whenthe wireless communication terminal compares the number of TIDs of theA-MPDU to be transmitted to the AP and the maximum number of TIDs, thewireless communication terminal may not calculate the TID with no BAagreement as the number of TIDs of the A-MPDU. That is because, sincethe recipient directly transmits the data corresponding to the TID withno BA agreement to the upper layer without storing the datacorresponding to the TID in the buffer, data reception corresponding tothe TID with no BA agreement may not affect the management of the scoreboard. Also, this is because, when the wireless communication terminalcalculates the TID with no BA agreement as the number of TIDs, thebuffer management and the A-MPDU configuration may be restricted.Specifically when the value of the TID Aggregation Limit field is 1 to6, the wireless communication terminal may generate an A-MPDU having thenumber of TIDs with BA agreement smaller than or equal to the value ofthe TID Aggregation Limit field, and may transmit the generated A-MPDUto the AP. At this time, the wireless communication terminal may add theMPDU corresponding to the TID with no BA agreement to the A-MPDUregardless of the value of the TID Aggregation Limit field. Further, theAP sets the value of the TID Aggregation Limit field of Per User Info ofthe trigger frame trigger frame to 0 to indicate that the wirelesscommunication terminal corresponding to the Per User Info field isallowed to aggregate MPDUs not requesting an immediate responseregardless of the TID with BA agreement to generate an A-MPDU andtransmit the generated A-MPDU to the AP. Specifically, when the TIDAggregation Limit field value of the User Info field corresponding tothe wireless communication terminal of the trigger frame is 0, thewireless communication terminal may generate an A-MPDU to be transmittedto the AP by aggregating MPDUs not requesting an immediate response.

In the embodiment of FIG. 9, the AP sets the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame to 3 to indicate that the maximumnumber of TIDs with BA agreement that the A-MPDU to be transmitted tothe AP by the third station STA3 is 3. The third station STA3 determinesthe number of TIDs with BA agreement of the A-MPDU to be transmitted tothe AP based on the value of the TID Aggregation Limit field of the UserInfo field corresponding to the third station of the trigger frame. Thethird station STA3 determines that the A-MPDU to be transmitted to theAP has three TIDs with BA agreement based on the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame. There is a BA agreement for TID 1,2, and 4, and there is no BA agreement for TID 5. Accordingly, the thirdstation STA1 aggregates an MPDU having a TID of 1, an MPDU having a TIDof 2, an MPDU having a TID of 3, an MPDU having a TID of 5, an action NoAck frame, and a QoS null frame to generate an A-MPDU to be transmittedto the AP. The third station STA3 transmits the generated A-MPDU to theAP. The AP transmits an M-BA frame to a plurality of wirelesscommunication terminals including the third station STA3 based on theA-MPDU received from the third station SAT3. Through this embodiment,the AP adjusts the duration of the M-BA frame.

Data corresponding to a TID with no BA agreement may also request an ACKframe transmission. At this time, the recipient may transmit the M-BAframe including the Per AID TID field that does not include the BAbitmap in response to the MPDU corresponding to the TID with no BAagreement. Therefore, even the MPDU corresponding to the TID with no BAagreement may affect the duration of the M-BA frame. Thus, the maximumnumber of TIDs that an A-MPDU may have may be calculated based on thenumber of TIDs requesting an immediate response and the number of frameswithout a TID requesting an immediate response. This will be describedin more detail with reference to FIG. 10.

FIG. 10 shows an operation of a wireless communication terminalaccording to another embodiment of the present invention to transmit anA-MPDU based on the maximum number of TIDs information.

The AP may use the trigger frame to limit the number of MPDUs requestingan immediate response that an A-MPDU to be transmitted by a wirelesscommunication terminal may have. The AP may use the trigger frame tolimit the number of MPDUs requesting an immediate response that anA-MPDU to be transmitted by a wireless communication terminal is capableof having. The wireless communication terminal may calculate the numberof TIDs of the A-MPDU based on the number of TIDs requesting animmediate response. In the embodiments described above, when thewireless communication terminal compares the number of TIDs of theA-MPDU to be transmitted to the AP and the maximum number of TIDs, thewireless communication terminal may compare the number of TIDsrequesting an immediate response of the A-MPDU to the maximum number ofTIDs. When the wireless communication terminal compares the number ofTIDs of the A-MPDU to be transmitted to the AP and the maximum number ofTIDs, it is possible to calculate the number of TIDs of the A-MPDUwithout considering an MPDU not requesting an immediate response.Therefore, the wireless communication terminal may aggregate MPDUscorresponding to TIDs not requesting an immediate response regardless ofthe maximum number of TIDs. Also, the wireless communication terminalmay aggregate frames without a TID not requesting an immediate responseregardless of the maximum number of TIDs. Also, the number of TIDsrequesting an immediate response may be the sum of the number of frameshaving no TID requesting an immediate response included in the A-MPDUand the number of TIDs requesting an immediate response included in theA-MPDU. The number of frames without a TID may indicate the type offrame without a TID. Also, an action frame in which the TID is 15 in theper AID TID field of the M-BA frame may be one of frames without a TIDrequesting an immediate response. The MPDU corresponding to the TID notrequesting an immediate response may be the MPDU corresponding to theTID in which ACK policy is set to No Ack. Also, an MPDU corresponding toa TID not requesting an immediate response may be a QoS null frame. Atthis time, the ACK policy of the QoS Null frame may be No Ack. Also, aframe without a TID not requesting an immediate response may be anAction No Ack frame.

As described above, the AP sets the value of the TID Aggregation Limitfield of Per User Info of the trigger frame trigger frame to 0 toindicate that the wireless communication terminal corresponding to thePer User Info field is allowed to aggregate MPDUs not requesting animmediate response regardless of the TID with BA agreement to generatean A-MPDU and transmit the generated A-MPDU to the AP. Specifically,when the TID Aggregation Limit field value of the User Info fieldcorresponding to the wireless communication terminal of the triggerframe is 0, the wireless communication terminal may generate an A-MPDUto be transmitted to the AP by aggregating MPDUs not requesting animmediate response.

In the embodiment of FIG. 10, the AP sets the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame to 3 to indicate that the maximumvalue of the sum of the number of TIDs that the A-MPDU to be transmittedto the AP by the third station STA3 may have and the number of frameswithout a TID requesting an immediate response included in the A-MPDU is3. The third station STA3 determines the number of sums of the number ofTIDs requesting an immediate response of the A-MPDU to be transmitted tothe AP and the number of frames without a TID requesting an immediateresponse based on the value of the TID Aggregation Limit field of theUser Info field corresponding to the third station of the trigger frame.The third station STA3 determines as 3 the sum of the number of TIDsrequesting an immediate response of the A-MPDU to be transmitted to theAP and the number of frames without a TID requesting an immediateresponse based on the value of the TID Aggregation Limit field of theUser Info field corresponding to the third station of the trigger frame.TIDs 1 and 2 request an immediate response, and TIDs 4 and 5 have theACK policy set to No Ack. Also, the action frame requests an immediateresponse. Accordingly, the third station STA1 aggregates an MPDU havinga TID of 1, an MPDU having a TID of 2, an MPDU having a TID of 4, anMPDU having a TID of 5, an action frame, an action No Ack frame, and aQoS null frame to generate an A-MPDU to be transmitted to the AP. Thethird station STA3 transmits the generated A-MPDU to the AP. The APtransmits an M-BA frame to a plurality of wireless communicationterminals including the third station STA3 based on the A-MPDU receivedfrom the third station SATS. Through this embodiment, the AP adjusts theduration of the M-BA frame.

FIG. 11 shows an operation of a wireless communication terminalaccording to another embodiment of the present invention to transmit anA-MPDU based on the maximum number of TIDs information.

The Multi-TID A-MPDU may not include a plurality of action frames.Accordingly, the Multi-TID A-MPDU may include only one action frame.Also, when the A-MPDU additionally includes an action frame, the lengthof the M-BA frame is increased by two octets. Therefore, the change inthe M-BA duration due to the addition of the action frame to the A-MPDUis insignificant. Also, it may be seen that the action frame is moreimportant than the QoS data frame.

When the wireless communication terminal compares the number of TIDs ofthe A-MPDU to be transmitted to the AP and the maximum number of TIDs,the wireless communication terminal may not calculate the number ofaction frames as the number of TIDs of the A-MPDU. Specifically, whenthe value of the TID Aggregation Limit field is within a predeterminedrange, the wireless communication terminal may generate an A-MPDU to betransmitted to the AP by aggregating action frames regardless of thevalue of the TID Aggregation Limit field. Specifically, in theembodiments of FIGS. 8 to 10, the wireless communication terminal maynot calculate the number of action frames as the number of TIDs of theA-MPDU.

In the embodiment of FIG. 11, the AP sets the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame to 2 to indicate that the maximumvalue of the sum of the number of TIDs that the A-MPDU to be transmittedto the AP by the third station STA3 is capable of having and the numberof frames without a TID requesting an immediate response included in theA-MPDU excluding an action frame is 3. At this time, the action frame isexcluded from the maximum value calculation. The third station STA3determines the number of sums of the number of TIDs requesting animmediate response of the A-MPDU to be transmitted to the AP and thenumber of frames without a TID requesting an immediate response includedin the A-MPDU excluding an action frame based on the value of the TIDAggregation Limit field of the User Info field corresponding to thethird station of the trigger frame. The third station STA3 determinesthat the A-MPDU to be transmitted to the AP has two TIDs requesting animmediate response based on the value of the TID Aggregation Limit fieldof the User Info field corresponding to the third station of the triggerframe. TIDs 1 and 2 request an immediate response, and TIDs 4 and 5 havethe ACK policy set to No Ack. Also, action frames are excluded fromcounting. Accordingly, the third station STA1 aggregates an MPDU havinga TID of 1, an MPDU having a TID of 2, an MPDU having a TID of 4, anMPDU having a TID of 5, an action frame, an action No Ack frame, and aQoS null frame to generate an A-MPDU to be transmitted to the AP. Thethird station STA3 transmits the generated A-MPDU to the AP. The APtransmits an M-BA frame to a plurality of wireless communicationterminals including the third station STA3 based on the A-MPDU receivedfrom the third station SAT3. Through this embodiment, the AP adjusts theduration of the M-BA frame.

The AP may use the trigger information to instruct the wirelesscommunication terminal transmitting the response to the triggerinformation to perform channel sensing before transmitting the response.Specifically, the AP may set the CS Required field value of the triggerinformation to instruct the wireless communication terminal transmittingthe response to the trigger information to perform channel sensingbefore transmitting the response. The CS Required field indicateswhether channel sensing is required when the wireless communicationterminal transmits a response to the trigger information. At this time,when the value of the CS Required field is 1, the CS Required field mayindicate that channel sensing is required. In addition, whentransmitting the response to the trigger information, the wirelesscommunication terminal receiving the trigger information may determinewhether to perform channel sensing based on the CS Required field of thetrigger information. Specifically, when the value of the CS Requiredfield of the trigger information is 1, the wireless communicationterminal receiving the trigger information may perform channel sensingwhen transmitting a response to the trigger information. At this time,the channel sensing may indicate whether the channel to transmit theresponse to the trigger information is idle or not. Also, channelsensing may indicate CCA operation.

FIG. 12 shows an operation of a wireless communication terminalaccording to an embodiment of the present invention to set the maximumnumber of TIDs information of a trigger frame.

When the AP triggers an immediate response to the data transmissionusing the trigger information, the AP may use the trigger information toindicate that no channel sensing is required when the wirelesscommunication terminal transmits a response to the trigger information.Specifically, when the AP triggers an immediate response to the datatransmission using the trigger information and the value of the lengthfield of the common info field of the trigger information is less thanor equal to the predetermined value, the AP may use the triggerinformation to indicate that no channel sensing is required when thewireless communication terminal transmits a response to the triggerinformation. At this time, the length field indicates information on thelength of the trigger-based PPDU. Specifically, the length field mayindicate information on the length of the trigger-based PPDU. Inaddition, the predetermined value may be 418 bytes. Through this, the APmay prevent the wireless communication terminal transmitting theresponse to the trigger information from not transmitting an immediateresponse due to the channel sensing. At this time, there is anoperational problem that the wireless communication terminal transmits aresponse to the trigger information and data together. This is because,when a wireless communication terminal operating as an EDCA transmitsdata, the wireless communication terminal may be required to transmitdata after performing channel sensing. Further, this is because, when awireless communication terminal transmitting a response to the triggerinformation transmits an MPDU requesting an immediate response, anadditional transmission sequence is required.

In the case where channel sensing is not required when the wirelesscommunication terminal indicated by the trigger frame transmits aresponse to the trigger information, the AP may use the trigger frame toindicate that the wireless communication terminals indicated by thetrigger frame is not allow to aggregate the MPDUs requesting animmediate response to generate an A-MPDU and transmit the generatedA-MPDU. Specifically, in the case where channel sensing is not requiredwhen the wireless communication terminal indicated by the trigger frametransmits a response to the trigger information, the AP may set thevalue of the TID Aggregation Limit field of the User Info field of thetrigger frame to 0 to indicate that the wireless communication terminalcorresponding to the User Info field is not allowed to aggregate theMPDUs requesting an immediate response to generate an A-MPDU.Specifically, when the AP triggers an immediate response to the datatransmission using the trigger information and the value of the lengthfield of the common info field of the trigger information is less thanor equal to the predetermined value, it may indicate that the wirelesscommunication terminal indicated by the trigger frame is not allowed toaggregate the MPDUs requesting an immediate response to generate anA-MPDU and transmit the generated A-MPDU. In these embodiments, thewireless communication terminal may aggregate MPDUs not requesting animmediate response to generate an A-MPDU and transmit the generatedA-MPDU to the AP.

In the embodiment of FIG. 12, the AP transmits HE MU PPDU to a pluralityof stations. At this time, the HE MU PPDU includes a trigger framerequesting an immediate response to the data MPDU included in the HE MUPPDU. Also, the value of the length field of the Common Info field ofthe trigger frame is 418. In addition, the CS required bit of thetrigger frame is set to 0. Therefore, the AP sets the value of the TIDAggregation Limit field of the User Info field of the trigger frame to0. The wireless communication terminal receiving the trigger frametransmits a response to the data MPDU included in the HE MU PPDU and anA-MPDU including the MPDU not requesting an immediate response together.At this time, the value of the length field of the trigger frametriggering the trigger-based PPDU (HE TB PPDU) including the A-MPDU isless than or equal to 418. Therefore, the first station transmits theA-MPDU including the MPDU including the BA frame and the data in whichthe ACK Policy is No Ack. The second station transmits an A-MPDUincluding a BA frame and an action No Ack frame. The third station andthe fourth station transmit an A-MPDU including a BA frame and a QoSnull frame.

Through FIGS. 7 to 12, an operation in which the AP triggers the A-MPDUtransmission of the wireless communication terminal using the triggerframe has been described. As described above, the AP may use the MACheader to trigger the wireless communication terminal to transmit thetrigger-based PPDU to the AP. Specifically, the AP may insert thetrigger information into the HE variant HT control field of the MACheader to trigger the wireless communication terminal to transmit thetrigger-based PPDU to the AP. At this time, the trigger informationincluded in the MAC header is referred to as UL MU response scheduling(UL MU RS). Through FIGS. 13 to 15, an operation in which the APtriggers the wireless communication terminal to transmit thetrigger-based PPDU including the A-MPDU using the UL MU RS will bedescribed.

FIG. 13 describes an operation in which a wireless communicationterminal according to an embodiment of the present invention transmitsan A-MPDU based on UL MU RS.

Since the UL MU RS is included in the MAC header, the size of the fieldthat may be used by the UL MU RS may be limited. Specifically, the UL MURS is identified by a 4-bit Control ID field in the HE variant HTcontrol field and may indicate the trigger information using a 26-bitfield. In addition, the UL MU RS may trigger an ACK/BA frametransmission for the payload included in the MAC frame including the ULMU RS. In addition, the UL MU RS may trigger the transmission of thewireless communication terminal corresponding to the recipient addressin the MAC frame including the UL MU RS. In these embodiments, the UL MURS may include less information than the trigger frame. Therefore, theUL MU RS may not include the maximum number of TIDs information. Thewireless communication terminal receiving the MAC frame including the ULMU RS may transmit the Trigger Based PPDU (TB PPDU) within the UL PPDUlength indicated by the UL MU RS. Accordingly, the wirelesscommunication terminal receiving the MAC frame including the UL MU RSmay generate the A-MPDU to be transmitted to the AP regardless of thenumber of TIDs that the A-MPDU is capable of having.

In the embodiment of FIG. 13, the AP transmits an HE MU PPDU including adata MPDU for each of the first station STA1 to the third station STA3and a broadcast trigger frame. At this time, the MAC header of the dataMPDU for each of the first station STA1 to the third station STA3includes UL MU RS. Each of the first to third stations STA1 to STA3generates an A-MPDU including an ACK/BA frame, a data MPDU, and an MPDUbased on UL MU RS. Each of the first to third stations STA1 to STA3transmits the generated A-MPDU to the AP using the HE MU PPDU. The firststation STA1 aggregates an ACK/BA frame, an MPDU corresponding to eachof a plurality of TIDs, and an MMPDU to generate an A-MPDU.

When a wireless communication terminal receiving a MAC frame includingan UL MU RS transmits an A-MPDU having a TID exceeding the total numberof TIDs that the AP may receive to the AP, the AP may not receive theA-MPDU or may malfunction. Accordingly, there is a need for a method toprevent this.

FIG. 14 describes an operation in which a wireless communicationterminal according to another embodiment of the present inventiontransmits an A-MPDU based on UL MU RS.

As described above, the wireless communication terminal receiving the ULMU RS may generate the A-MPDU including the ACK/BA frame. The wirelesscommunication terminal receiving the UL MU RS may transmit the generatedA-MPDU to the AP using the information indicated by the UL MU RS. Atthis time, the MPDU that the wireless communication terminal receivingthe UL MU RS may aggregate with the ACK/BA frame may be limited to atleast one of the MPDU corresponding to one TID and one MMPDU.Accordingly, the wireless communication terminal receiving the UL MU RSmay generate the A-MPDU by aggregating the ACK/BA frame with at leastone of the MPDU corresponding to one TID and one MMPDU. At this time,the M-BA frame transmitted by the AP may include at most two BAinformation fields per wireless communication terminal. This is becausethe MMPDU in the M-BA frame is treated as having a TID of 1111. In theembodiment of FIG. 14, the AP transmits the HE MU PPDU to the firststation STA1 to the third station STA3 as in the embodiment of FIG. 13.At this time, the first station STA1 transmits the A-MPDU to the APbased on the UL MU RS included in the MAC frame transmitted to the firststation STA1. In the embodiment of FIG. 14(a), the first station STA1aggregates an ACK/BA frame, an MPDU corresponding to a TID of 3, and anMMPDU to generate an A-MPDU.

In another specific embodiment, the MPDU that the wireless communicationterminal receiving the UL MU RS is capable of aggregating with theACK/BA frame may be limited to any one of the MPDU corresponding to oneTID and one MMPDU. Accordingly, the wireless communication terminalreceiving the UL MU RS may generate the A-MPDU by aggregating the ACK/BAframe with any one of the MPDU corresponding to one TID and one MMPDU.At this time, the M-BA frame transmitted by the AP may include at mostone BA information field per wireless communication terminal. In theembodiment of FIG. 14(b), the first station STA1 aggregates an ACK/BAframe and an MPDU corresponding to a TID of 3 to generate an A-MPDU.

In another specific embodiment, the MPDU that the wireless communicationterminal receiving the UL MU RS may aggregate with the ACK/BA frame maybe limited to at least one of the MMPDU and the MPDU corresponding tothe high priority TID. Accordingly, the wireless communication terminalreceiving the UL MU RS may generate the A-MPDU by aggregating any one ofan ACK/BA frame, an MMPDU, and an MPDU having a high priority MPDU. Atthis time, a TID having a high preference may indicate a TID having apriority higher than a certain priority. Specifically, the certainpriority may be designated by the AP. In a specific embodiment, the APmay specify a certain priority in the link setup procedure. For example,the AP may designate a certain priority by using at least one of abeacon frame, an association response frame, and an authenticationresponse frame. In the embodiment of FIG. 14(c), the first station STA1generates an A-MPDU by aggregating an ACK/BA frame, an MPDU in which aTID having a priority higher than a certain priority corresponds to 1,and an MMPDU.

In another specific embodiment, the MPDU that the wireless communicationterminal receiving the UL MU RS may aggregate with the ACK/BA frame maybe limited to an MMPDU. Accordingly, the wireless communication terminalreceiving the UL MU RS may aggregate an ACK/BA frame and an MMPDU togenerate an A-MPDU. In the embodiment of FIG. 14(d), the first stationSTA1 aggregates an ACK/BA frame and an MPDU corresponding to a TID of 3to generate an A-MPDU.

In addition, the wireless communication terminal receiving the UL MU RSmay aggregate an ACK/BA frame and an MPDU corresponding to the TID withno BA agreement without limitation in the embodiments described above.

In another specific embodiment, the MPDU that the wireless communicationterminal receiving the UL MU RS may aggregate with the ACK/BA frame maybe limited to an MPDU not requesting an immediate response. Accordingly,the wireless communication terminal receiving the UL MU RS may aggregatean ACK/BA frame and an MPDU not requesting an immediate response togenerate an A-MPDU. In the embodiment of FIG. 14(e), the first stationSTA1 aggregates an ACK/BA frame and an MPDU not requesting an immediateresponse to generate an A-MPDU. The wireless communication terminal mayprevent the transmission sequence from being increased through such anembodiment.

In another specific embodiment, the wireless communication terminalreceiving the UL MU RS may transmit the A-MPDU including the ACK/BAframe without aggregating the ACK/BA frame with another MPDU. Thewireless communication terminal may maximize the reliability of ACK/BAframe transmission.

FIG. 15 describes an operation in which a wireless communicationterminal according to another embodiment of the present inventiontransmits an A-MPDU based on UL MU RS.

The AP may signal that the aggregation of ACK/BA frames and other MPDUstransmitted based on the UL MU RS is restricted while transmitting theUL MU RS. Specifically, the AP sets a bit indicating whether to allowthe aggregation of UL MU RS to 0 to signal that the aggregation ofACK/BA frames and other MPDUs transmitted based on the UL MU RS isrestricted. When UL MU RS indicates that the aggregation of ACK/BAframes and other MPDUs transmitted based on UL MU RS is restricted, thewireless communication terminal receiving the UL MU RS may generate theA-MPDU including the ACK/BA frame according to the various embodimentsdescribed with reference to FIG. 14. Specifically, when the UL MU RSindicates that the aggregation of the ACK/BA frames and other MPDUs isrestricted, the wireless communication terminal receiving the UL MU RSmay transmit the A-MPDU including the ACK/BA frame to the AP withoutaggregation with another MPDU. In another specific embodiment, when theUL MU RS indicates that the aggregation of the ACK/BA frames and otherMPDUs is restricted, the wireless communication terminal receiving theUL MU RS may transmit an A-MPDU including an ACK/BA frame and an MPDUnot requesting an immediate response to the AP.

In the embodiment of FIG. 15, the AP sets the value of the Aggregationallowed field included in the UL MU RS to indicate that the aggregationof ACK/BA frames and MPDUs transmitted based on UL MU RS is restricted.At this time, when the value of the Aggregation allowed field is 0, thefirst station STA1 transmits an A-MPDU including an ACK/BA frame andpadding to the AP. Also, when the value of the aggregation allowed fieldis 1, the first station STA1 transmits an A-MPDU including an ACK/BAframe, an MPDU with a TID of 1, and an MMPDU to the AP. Through thisembodiment, the form of the A-MPDU transmitted on the basis of the UL MURS may be varied.

When a Received Signal Strength Indication (RSSI) difference between theMU PPDUs transmitted by a plurality of wireless communication terminalsis large, it may be difficult for the AP to normally receive the MU PPDUfrom the plurality of wireless communication terminals. Thus, the AP mayuse the trigger information to adjust the transmission power of the MUPPDUs transmitted by each of the plurality of wireless communicationterminals. This will be described with reference to FIGS. 16 to 23.

FIG. 16 shows that an AP according to an embodiment of the presentinvention signals the transmission power of a trigger frame to aplurality of wireless communication terminals using a trigger frame, anda plurality of wireless communication terminals adjust the transmissionpower of an MU PPDU based on the transmission power of a trigger frame.

The size of the path loss occurring during transmission differsdepending on the location of the wireless communication terminal. Atthis time, the path loss indicates that the intensity of the signal isattenuated while the wireless signal is transmitted along a specificpath. In FIG. 16, the second station STA2 is located farther from the APthan the first station STA1, and the path loss PL2 generated duringtransmission between the second station STA2 and the AP is larger thanthe path loss PL1 generated during transmission between the firststation STA1 and the AP. Therefore, in order to adjust the RSSI of theMU PPDU received by the AP to the RSSI designated by the AP, thewireless communication terminal must calculate the path loss occurringin the transmission path from the wireless communication terminal to theAP. For this, the AP may insert information on the transmission powerfor transmitting the PPDU including the trigger information into thetrigger information. Specifically, the AP may insert the transmissionpower into at least one of the trigger frame and the UL MU RS. At thistime, the RSSI designated by the AP is referred to as a target RSSI. Inaddition, the transmission power for transmitting the PPDU includingtrigger information is referred to as DL TX power. For example, the APmay insert information on the DL TX power into the Common Info field ofthe trigger frame as shown in FIG. 16. In addition, the AP may insertinformation on the target RSSI into the Trigger Dependent Info field ofthe Per User Info field of the trigger frame as shown in FIG. 16. Inaddition, the AP may insert information on the DL TX power into the HEvariant HT control field as shown in FIG. 16. In addition, the AP mayinsert information on the target RSSI into the HE variant HT controlfield as shown in FIG.

16.

The wireless communication terminal may obtain information on the DL TXpower based on the trigger information received from the AP. Thewireless communication terminal may estimate the path loss occurring inthe transmission path between the wireless communication terminal andthe AP based on the RSSI of the PPDU including the DL TX power and thetrigger information. Specifically, the wireless communication terminalmay estimate the path loss occurring in the transmission path betweenthe wireless communication terminal and the AP by subtracting the RSSIof the PPDU including the trigger information from the DL TX power basedon the trigger information as shown in FIG. 16. Specifically, the DL TXpower may be displayed in 20 MHz units in the trigger information.

The wireless communication terminal may measure the RSSI of the PPDU inthe physical layer, and obtain information on the DL TX power andinformation on the target RSSI included in the trigger information fromthe MAC layer. At this time, the wireless communication terminalmeasures the RSSI in advance, and determines the transmission power ofthe trigger-based PPDU based on the information on the DL TX power andthe information on the target RSSI obtained in the MAC layer.Specifically, the wireless communication terminal adds the path lossoccurring in the transmission path between the AP and the wirelesscommunication terminal to the target RSSI based on RSSI and DL TX poweras shown in FIG. 16 to determine the transmission power (Target UL TXPower) of the trigger-based PPDU. The wireless communication terminaltransmits the trigger-based PPDU with the determined transmission power.

Even with the same PPDU, the size of the allocated power may varydepending on the frequency and time. Therefore, according to the methodof the wireless communication terminal to measure the RSSI of the PPDUincluding the trigger information, the path loss estimation occurring inthe transmission between the AP and the wireless communication terminalmay become inaccurate. Especially, when a PPDU including triggerinformation is transmitted through a bandwidth of 80 MHz or more and acenter 26 Resource Unit (RU) exists in the center of the 80 MHzbandwidth, the center 26 RU is located in the center of two consecutive20 MHz frequency bands. Specifically, the center 26 RU may indicate a RUthat includes subcarriers corresponding to indices from −16 to −4 andfrom 4 to 16 and 7 Direct Current (DC) subcarriers located at the centerof the frequency band. Therefore, it may be a problem that whichfrequency band's RSSI the wireless communication terminal that receivesthe payload of the PPDU through the center 26 RU should measure. Amethod of the wireless communication terminal to measure the RSSI of theMU PPDU will be described with reference to FIGS. 17 to 23. At thistime, the MU PPDU may include trigger information as described above.

FIG. 17 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to an embodiment of the presentinvention.

The wireless communication terminal may measure the RSSI of the legacypreamble of the PPDU transmitted on the primary channel having thebandwidth of 20 MHz as the RSSI of the PPDU. At this time, the legacypreamble indicates a preamble that may be decoded by not only thewireless communication terminal according to the embodiment of thepresent invention but also the legacy wireless communication terminal.Specifically, the wireless communication terminal may measure the RSSIof the legacy training field of the PPDU transmitted on the primarychannel having the bandwidth of 20 MHz as the RSSI of the PPDU. In aspecific embodiment, the wireless communication terminal may measure theRSSI of the Legacy-Long Training Field (L-LTF) transmitted on theprimary channel having a bandwidth of 20 MHz as the RSSI of the PPDU. Inanother specific embodiment, the wireless communication terminal maymeasure an average value of RSSI of an L-LTF and a legacy short trainingfield (L-STF) transmitted on a primary channel having a bandwidth of 20MHz as the RSSI of the PPDU. At this time, L-LTF indicates a longtraining signal, which is a training signal having a relatively longsignal length. Specifically, the wireless communication terminal mayestimate a frequency offset and a channel of an OFDM symbol including anL-SIG field based on the LTF. Also, L-STF indicates a short trainingsignal, which is a training signal having a relatively short length.Specifically, the wireless communication terminal may perform AutomaticGain Control (AGC) on an OFDM symbol including an L-LTF field and anL-SIG field based on L-STF. Also, the wireless communication terminalmay synchronize the timing and frequency with the OFDM symbol includingthe L-SIG field based on the L-STF. The wireless communication terminaladjusts the transmission power based on the RSSI of the PPDU measuredthrough the above-described embodiments.

In the embodiment of FIG. 17, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, a plurality of wireless communicationterminals measure the RSSI of L-STF and L-LTF transmitted through aprimary channel having a bandwidth of 20 MHz. The plurality of wirelesscommunication terminals estimate the path loss occurring in transmissionfrom the AP to each of the plurality of wireless communication terminalsbased on the measured RSSI and DL TX power. At this time, the pluralityof wireless communication terminals may obtain the DL TX power from thetrigger frame or the UL MU RS. The plurality of wireless communicationterminals determine the transmission power of the trigger-based PPDUbased on the estimated path loss and the target RSSI. The plurality ofwireless communication terminals transmit the trigger-based PPDU to theAP according to the trigger frame or the information indicated by the ULMU RS.

The wireless communication terminal detects a primary channel having abandwidth of 20 MHz regardless of the position of the RU to which thepayload received by the wireless communication terminal is transmitted.In addition, in the case of the legacy preamble, the PPDU may betransmitted with the same power in the frequency band in which the PPDUis transmitted. Therefore, when the wireless communication terminalmeasures the RSSI of the PPDU based on the legacy preamble transmittedthrough the 20 MHz band, the wireless communication terminal mayefficiently measure the RSSI of the PPDU. In addition, a wirelesscommunication terminal that receives the payload of the PPDU through thecenter 26 RU may also accurately measure the RSSI of the PPDU. Also, thewireless communication terminal may measure the RSSI of the PPDU in thesame manner when receiving the trigger frame transmitted in the form ofthe non-HT PPDU.

FIG. 18 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to another embodiment of the presentinvention.

The wireless communication terminal may measure the RSSI of the PPDU inthe entire frequency band in which the PPDU is transmitted. At thistime, the wireless communication terminal may average the RSSI measuredin the entire frequency band in which the PPDU is transmitted in unitsof 20 MHz. Specifically, the wireless communication terminal may measurethe RSSI of the legacy preamble as the RSSI of the PPDU in the entirefrequency band in which the PPDU is transmitted. Specifically, thewireless communication terminal may measure the RSSI of the PPDU basedon a value obtained by averaging the RSSI of the legacy preamble in theentire frequency band in which the PPDU is transmitted in units of 20MHz bandwidth. But, unlike the payload of PPDUs transmitted using 256FFTs, the legacy preamble is transmitted using 64 FFTs. Accordingly,when the wireless communication terminal measures the RSSI of the PPDUbased on the legacy preamble, an error may be generated accordingly.

The wireless communication terminal may measure the RSSI of the PPDUbased on the non-legacy training field. The wireless communicationterminal may measure the RSSI of the non-legacy training field as theRSSI of the PPDU in the entire frequency band in which the PPDU istransmitted. Specifically, the wireless communication terminal maymeasure the RSSI of the PPDU based on a value obtained by averaging theRSSI of the non-legacy training field in units of 20 MHz bandwidth inthe entire frequency band in which the PPDU is transmitted. In aspecific embodiment, the wireless communication terminal subtracts avalue obtained by averaging the RSSI of the non-legacy training field inunits of 20 MHz bandwidth in the entire frequency band in which the PPDUis transmitted from the DL TX power obtained from the triggerinformation, thereby estimating the path loss occurring in thetransmission path between the wireless communication terminal and theAP. In such embodiments, the wireless communication terminal may obtaininformation on the bandwidth of the PPDU signaling the MU PPDU tomeasure the RSSI of the non-legacy training field in the entirefrequency band in which the PPDU is transmitted. Also, the non-legacytraining field may be a non-legacy long training field. The wirelesscommunication terminal may estimate the frequency offset and channel ofthe OFDM symbol including the non-legacy signaling field and the payloadbased on the non-legacy long training field. Specifically, the wirelesscommunication terminal may estimate a channel in which data istransmitted based on a non-legacy long training field. Also, thewireless communication terminal may estimate the frequency offset of theOFDM symbol based on the non-legacy long training field. In addition,the wireless communication terminal may perform Automatic Gain Control(AGC) on an OFDM symbol including a non-legacy long training field, anon-legacy signaling field, and a payload based on a short trainingsignal. In addition, the wireless communication terminal may performsynchronization on the timing and frequency of the OFDM symbolsincluding the non-legacy long training field, the non-legacy signalingfield and the payload based on the non-legacy short training field.

In the embodiment of FIG. 18, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, a plurality of wireless communicationterminals cross-correlate HE-LTF, which is a non-legacy long trainingfield, to measure the RSSI of the HE-LTF. The plurality of wirelesscommunication terminals estimate the path loss occurring in transmissionfrom the AP to each of the plurality of wireless communication terminalsbased on the measured RSSI and DL TX power. Other operations of theplurality of wireless communication terminals may be the same as thosedescribed in the embodiment of FIG. 17.

However, when an AP transmits an HE MU PPDU using OFDMA, the AP may settransmission power differently for each RU. Specifically, when the APtransmits the HE MU PPDU using the OFDMA, the AP may set thetransmission power differently for each RU from HE-STF, which is thenon-legacy short training field. In particular, when 256 FFTs are used,the effect of frequency selectivity for each RU may be greater. The RSSImeasurement method considering the transmission power difference foreach RU will be described with reference to FIG. 19.

FIG. 19 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to another embodiment of the presentinvention.

The wireless communication terminal may measure the RSSI of thenon-legacy training field as the RSSI of the PPDU in the RU throughwhich the payload of the PPDU is transmitted, which corresponds to thewireless communication terminal. At this time, the non-legacy trainingfield may be HE-LTF, which is a non-legacy long training field. Inaddition, the RU through which the payload of the PPDU is transmittedmay indicate a RU through which a trigger frame for triggering thewireless communication terminal or UL MU RS is transmitted.Specifically, when the bandwidth of the RU through which the payload ofthe PPDU is transmitted is smaller than 20 MHz, the wirelesscommunication terminal may scale the measured RSSI in units of 20 MHz.

In the embodiment of FIG. 19, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, a plurality of wireless communicationterminals cross-correlate HE-LTF to measure the RSSI of the HE-LTF in aRU through which a payload for each of the plurality of wirelesscommunication terminal is transmitted. The plurality of wirelesscommunication terminals estimate the path loss occurring in transmissionfrom the AP to each of the plurality of wireless communication terminalsbased on the measured RSSI and DL TX power. At this time, when thebandwidth of the RU is smaller than 20 MHz, the measured RSSI value maybe scaled in units of 20 MHz. Other operations of the plurality ofwireless communication terminals may be the same as those described inthe embodiment of FIG. 17.

In this embodiment, when the frequency band of the RU through which thepayload of the PPDU corresponding to the wireless communication terminalis transmitted is too narrow, the number of sample symbols that thewireless communication terminal may use to measure the RSSI may beexcessively small. Accordingly, the accuracy of the RSSI measured by thewireless communication terminal may deteriorate.

FIG. 20 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to another embodiment of the presentinvention.

The wireless communication terminal may measure the RSSI of thenon-legacy training field as the RSSI of the PPDU in a frequency with a20 MHz bandwidth including a RU through which the payload of the PPDU istransmitted, which corresponds to the wireless communication terminal.At this time, the non-legacy training field may be HE-LTF, which is anon-legacy long training field. In addition, the RU through which thepayload of the PPDU is transmitted may indicate a RU through which atrigger frame for triggering the wireless communication terminal or ULMU RS is transmitted.

In the embodiment of FIG. 20, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, a plurality of wireless communicationterminals cross-correlate HE-LTF to measure the RSSI of the HE-LTF in afrequency band with a 20 MHz bandwidth including an RU through which apayload for each of the plurality of wireless communication terminal istransmitted. The plurality of wireless communication terminals estimatethe path loss occurring in transmission from the AP to each of theplurality of wireless communication terminals based on the measured RSSIand DL TX power. At this time, when the bandwidth of the RU is smallerthan 20 MHz, the measured RSSI value may be scaled in units of 20 MHz.Other operations of the plurality of wireless communication terminalsmay be the same as those described in the embodiment of FIG. 17.

In such an embodiment, it may be a problem that in which frequency bandthe wireless communication terminal receiving the payload of the PPDUthrough the center 26 RU should measure the RSSI of the non-legacysignaling field.

FIG. 21 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to another embodiment of the presentinvention.

In the embodiments described above, when the wireless communicationterminal receives the payload of the PPDU through the center 26 RU, thewireless communication terminal may measure the RSSI of the non-legacysignaling field in the frequency band in which the SIG-B content channelsignaling information on the center 26 RU is transmitted. Specifically,the HE-SIG-B signaling field signals information on a plurality ofwireless communication terminals receiving the HE MU PPDU. Specifically,the information on a plurality of wireless communication terminals mayinclude information on resource allocation. At this time, theinformation on the resource allocation may include information on an RUthat a plurality of wireless communication terminals receive the payloadof the HE MU PPDU. The AP transmits an HE-SIG-B field includingdifferent information for each 20 MHz frequency band. Specifically, whenan AP transmits an HE MU PPDU through a frequency band having abandwidth of 40 MHz or more, the AP repeatedly transmits a first SIG-Bcontent channel having a bandwidth of 20 MHz and a second SIG-B contentchannel having a bandwidth of 20 MHz every 40 MHz bandwidth. At thistime, the AP transmits information on the center 26 RU of the primarychannel having the 80 MHz bandwidth through the first SIG-B contentchannel. In addition, the AP transmits information on the center 26 RUof the subchannel having the 80 MHz bandwidth through the second SIG-Bcontent channel. Therefore, when the wireless communication terminalreceives the payload of the PPDU through the center 26 RU included inthe primary channel having the bandwidth of 80 MHz, the wirelesscommunication terminal may measure the RSSI of the non-legacy signalingfield in the frequency band in which the first SIG-B content channel istransmitted. In addition, when the wireless communication terminalreceives the payload of the PPDU through the center 26 RU included inthe subchannel having the bandwidth of 80 MHz, the wirelesscommunication terminal may measure the RSSI of the non-legacy signalingfield in the frequency band in which the second SIG-B content channel istransmitted. In addition, the non-legacy training field may be HE-LTF,which is a non-legacy long training field.

In the embodiment of FIG. 21, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, the wireless communication terminalreceiving the payload through the center 26 RU measures the RSSI of theHE-LTF by cross-correlating the HE-LTF in the frequency band having the20 MHz bandwidth in which the first SIG-B content channel istransmitted. The wireless communication terminal estimate the path lossoccurring in transmission from the AP to the wireless communicationterminal based on the measured RSSI and DL TX power. In addition, thewireless communication terminal may obtain the DL TX power from thetrigger frame or the UL MU RS. The plurality of wireless communicationterminals determine the transmission power of the trigger-based PPDUbased on the estimated path loss and the target RSSI. The plurality ofwireless communication terminals transmit the trigger-based PPDU to theAP according to the trigger frame or the information indicated by the ULMU RS.

When the wireless communication terminal measures the RSSI of thenon-legacy signaling field in the frequency band in which the SIG-Bcontent channel for signaling the information on the center 26 RU istransmitted, the wireless communication terminal may obtain the HE-SIG-Bfield and measure the RSSI in the same frequency band. However, there isa disadvantage that the payload received by the wireless communicationterminal is not transmitted in the frequency band in which the wirelesscommunication terminal measures the RSSI.

FIG. 22 shows a method of a wireless communication terminal to measurethe RSSI of a MU PPDU according to another embodiment of the presentinvention.

In the embodiments described above, when the wireless communicationterminal receives the payload of the PPDU through the center 26 RU, thewireless communication terminal may measure the RSSI of the non-legacysignaling field in a frequency band close to the SIG-B content channelthat signals information on the center 26 RU among two frequency bandshaving a 20 MHz bandwidth including the center 26 RU. In anotherspecific embodiment, the wireless communication terminal may measure theRSSI of the non-legacy signaling field in two frequency bands having a20 MHz bandwidth including the center 26 RU. At this time, the wirelesscommunication terminal may average the measured RSSI in units of 20 MHz.In addition, the non-legacy training field may be HE-LTF, which is anon-legacy long training field.

In the embodiment of FIG. 22, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, the wireless communication terminalreceiving the payload through the center 26 RU may measure the RSSI ofthe HE-LTF by cross-correlating the HE-LTF in the frequency band closeto the first SIG-B content channel among the two frequency bands havingthe 20 MHz bandwidth including the center 26 RU. In another specificembodiment, at this time, the wireless communication terminal receivingthe payload through the center 26 RU may measure the RSSI of the HE-LTFby cross-correlating the HE-LTF in the two frequency bands having the 20MHz bandwidth including the center 26 RU, and average the RSSI in unitsof 20 MHz. Other operations of a wireless communication terminal may bethe same as those described in the embodiment of FIG. 21.

FIG. 23 shows a method of a wireless communication terminal to measurethe RSSI of an MU PPDU according to another embodiment of the presentinvention.

It may be restricted that the AP transmits trigger information throughthe center 26 RU. Specifically, the AP may not transmit triggerinformation through the center 26 RU. Specifically, the AP may nottransmit a trigger frame through the center 26 RU. In addition, the APmay not transmit the UL MU RS through the center 26 RU. This is becausethe center 26 RU is used only when the bandwidth of the frequency bandis over 80 MHz, and the size occupied by the center 26 RU is not largein the entire frequency band.

In the embodiment of FIG. 23, the AP transmits an HE MU PPDU having an80 MHz bandwidth including the center 26 RU to a plurality of wirelesscommunication terminals. The HE MU PPDU includes L-STF, L-LTF, L-SIG,RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF, payload Data, and packetextension PE. At this time, the AP transmits the payload of the PPDU,which does not include the trigger information, through the center 26RU. In such an embodiment, the AP may prevent a problem that may occurwhen the wireless communication terminal receiving the payload of thePPDU through the center 26 RU measures the RSSI of the non-legacysignaling field.

FIG. 24 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

The base wireless communication terminal 2401 transmits the triggerinformation to one or a plurality of wireless communication terminals2403 (S2401). At this time, the trigger information may be the triggerframe or UL MU RS described above.

The trigger information is a trigger frame, and the trigger frame mayinclude a first signaling field indicating information on the type ofMPDU included in the A-MPDU. At this time, when the wirelesscommunication terminal 2403 is not allowed to aggregate the MPDUrequesting the immediate response and generate the A-MPDU to betransmitted to the base wireless communication terminal 2401, the basewireless communication terminal 2401 may set the value of the firstsignaling field to a predetermined value. Also, when the base wirelesscommunication terminal 2401 is allowed for the wireless communicationterminal corresponding to the first signaling field to aggregate theMPDU requesting the immediate response and generate the A-MPDU to betransmitted to the base wireless communication terminal 2401, the basewireless communication terminal 2401 may set the value of the firstsignaling field according to the maximum number of TIDs that the A-MPDUis capable of having. The maximum number of TIDs that an A-MPDU iscapable of having may indicate the maximum number of TIDs that requestan immediate response that an A-MPDU is capable of having. The maximumnumber of TIDs requesting an immediate response may indicate the maximumvalue of the sum of the number of TIDs requesting an immediate responseand the number of frames without a TID requesting an immediate response.In another specific embodiment, the maximum number of TIDs that anA-MPDU is capable of having may indicate the maximum number of TIDs withBA agreement.

At this time, an immediate response may indicate that the recipienttransmits a response to the originator within a predetermined timeperiod in the same TXOP. Specifically, the predetermined period may be aShort Inter-Frame Space (SIFS). The MPDU corresponding to the TID notrequesting an immediate response may be the MPDU corresponding to theTID in which ACK policy is set to No Ack. Also, an MPDU corresponding toa TID not requesting an immediate response may be a QoS null frame. Atthis time, the ACK policy of the QoS Null frame may be No Ack. Also, aframe without a TID not requesting an immediate response may be anAction No Ack frame.

The trigger frame may include a second signaling field indicatingwhether channel sensing is required when the wireless communicationterminal 2403 transmits the trigger-based PPDU. The base wirelesscommunication terminal 2401 may set the value of the first signalingfield based on the value of the second signaling field. Specifically,when the second signaling field is set to indicate that channel sensingfor trigger-based PPDU transmission is not required, the base wirelesscommunication terminal 2401 may set the value of the first signalingfield to a predetermined value. The trigger frame may include a thirdsignaling field indicating information on the length of thetrigger-based PPDU. At this time, the base wireless communicationterminal may set the value of the first signaling field based on thevalue of the third signaling field. Specifically, when the value of thethird signaling field is less than a predetermined length, the basewireless communication terminal 2401 may set the value of the firstsignaling field to a predetermined value. The predetermined value is avalue indicating that the A-MPDU to be transmitted to the base wirelesscommunication terminal 2401 may not be generated by aggregating the MPDUrequesting the immediate response.

The first signaling field may be the TID Aggregation Limit fielddescribed above. Also, the second signaling field may be the CS requiredfield described above. In addition, the base wireless communicationterminal 2401 may operate according to the embodiments described withreference to FIGS. 8 to 15.

The wireless communication terminal 2403 transmits the A-MPDU based onthe trigger information (2403). The wireless communication terminal 2403may determine whether to aggregate MPDUs that request an immediateresponse and generate an A-MPDU based on the trigger information. Thetrigger frame may include a signaling field indicating whether thewireless communication terminal 2403 is allowed to aggregate the MPDUsrequesting an immediate response and generate an A-MPDU to betransmitted to the base wireless communication terminal 2401. Thewireless communication terminal 2403 may aggregate the MPDU requestingan immediate response based on the signaling field and generate anA-MPDU to be transmitted to the base wireless communication terminal2401. When the value of the signaling field is a predetermined value,the wireless communication terminal 2403 may generate the A-MPDU notincluding the MPDU requesting an immediate response. Further, when thevalue of the signaling field is within the predetermined range, thesignaling field indicates the maximum number of TIDs that the A-MPDU iscapable of having when generating the A-MPDU to be transmitted to thebase wireless communication terminal 2401 by the wireless communicationterminal 2403, the wireless communication terminal 2403 may generate anA-MPDU to be transmitted to the base wireless communication terminal2401 according to the maximum number of TIDs. When the value of thesignaling field is within a predetermined range, the wirelesscommunication terminal 2403 may generate an A-MPDU by aggregating MPDUsnot requesting an immediate response regardless of the maximum number ofTIDs that the A-MPDU is capable of having. An MPDU not requesting animmediate response may include a Quality of Service (QoS) Null frame notrequesting an ACK for data transmission. In addition, an MPDU notrequesting an immediate response may include an Action No Ack frame notrequesting an ACK for data transmission. In addition, an MPDU requestingan immediate response may include an action frame. In addition, when thevalue of the signaling field is within a predetermined range, thewireless communication terminal 2403 may generate an A-MPDU byaggregating action frames regardless of the maximum number of TIDs thatthe A-MPDU is capable of having. In addition, the signaling field may bethe TID Aggregation Limit field described above. The above-describedpredetermined value may be 0. In addition, the predetermined range maybe 1 or more. In addition, the wireless communication terminal 2403 mayoperate in the same manner as the embodiments described with referenceto FIGS. 8 to 12.

When the trigger information is included in the MAC header, the wirelesscommunication terminal 2403 may generate an A-MPDU that does not includean MPDU requesting an immediate response, as an A-MPDU to be transmittedto the base wireless communication terminal 2401. At this time, thetrigger information may be included in the HE variant HT control fieldof the MAC header. Specifically, the trigger information may be the ULMU RS described above. In a specific embodiment, when the triggerinformation is included in the MAC header, the wireless communicationterminal 2403 may aggregate any one frame of an ACK frame and a BlockACK (BA) frame and MPDUs not requesting an immediate response without anMPDU requesting an immediate response to generate the A-MPDU. At thistime, the MPDU not requesting an immediate response may include at leastone of a QoS Null frame not requesting an ACK for data transmission andan Action No Ack frame not requesting an ACK for data transmission.Specifically, the wireless communication terminal 2403 may operate as inthe embodiments described with reference to FIGS. 13 to 15.

The wireless communication terminal 2403 may measure the RSSI of thePPDU including the trigger frame and determine the transmission power ofthe trigger-based PPDU based on the measured signal strength.Specifically, the wireless communication terminal 2403 may measure theRSSI of the legacy preamble of the PPDU transmitted on the primarychannel having the bandwidth of 20 MHz as the RSSI of the PPDU. At thistime, the legacy preamble indicates a preamble that may be decoded bynot only the wireless communication terminal according to the embodimentof the present invention but also the legacy wireless communicationterminal.

In addition, the wireless communication terminal 2403 may measure theRSSI of the PPDU in the entire frequency band in which the PPDU istransmitted. At this time, the wireless communication terminal 2403 mayaverage the RSSI measured in the entire frequency band in which the PPDUis transmitted in units of 20 MHz. Specifically, the wirelesscommunication terminal 2403 may measure the RSSI of the legacy preambleas the RSSI of the PPDU in the entire frequency band in which the PPDUis transmitted. The wireless communication terminal 2403 may measure theRSSI of the PPDU based on the non-legacy training field.

In addition, the wireless communication terminal 2403 may measure theRSSI of the non-legacy training field as the RSSI of the PPDU in theentire frequency band in which the PPDU is transmitted. Specifically,the wireless communication terminal 2403 may measure the RSSI of thePPDU based on a value obtained by averaging the RSSI of the non-legacytraining field in units of 20 MHz bandwidth in the entire frequency bandin which the PPDU is transmitted.

In addition, the wireless communication terminal 2403 may measure theRSSI of the non-legacy training field as the RSSI of the PPDU in afrequency with a 20 MHz bandwidth including a RU through which thepayload of the PPDU is transmitted, which corresponds to the wirelesscommunication terminal. When the wireless communication terminal 2403receives the payload of the PPDU through the center 26 RU, the wirelesscommunication terminal 2403 may measure the RSSI of the non-legacysignaling field in the frequency band in which the SIG-B content channelsignaling information on the center 26 RU is transmitted. When thewireless communication terminal 2403 receives the payload of the PPDUthrough the center 26 RU, the wireless communication terminal 2403 maymeasure the RSSI of the non-legacy signaling field in a frequency bandclose to the SIG-B content channel that signals information on thecenter 26 RU among two frequency bands having a 20 MHz bandwidthincluding the center 26 RU. In another specific embodiment, the wirelesscommunication terminal 2403 may measure the RSSI of the non-legacysignaling field in two frequency bands having a 20 MHz bandwidthincluding the center 26 RU. At this time, the wireless communicationterminal 2403 may average the measured RSSI in units of 20 MHz. Inanother specific embodiment, it may be restricted that the base wirelesscommunication terminal 2401 transmits trigger information through thecenter 26 RU. Specifically, the base wireless communication terminal2401 may not transmit the trigger information through the center 26 RU.Specifically, the base wireless communication terminal 2401 may nottransmit the trigger frame through the center 26 RU. Specifically, thewireless communication terminal 2403 and the base wireless communicationterminal 2401 may operate as in the embodiments described with referenceto FIGS. 16 to 23.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

1-20. (canceled)
 21. A wireless communication terminal communicatingwirelessly, the terminal comprising: a transceiver; and a processor,wherein the processor is configured to: receive trigger information froma base wireless communication terminal using the transceiver, whereinthe trigger information triggers a transmission of a trigger-basedphysical layer protocol data unit (PPDU) by the wireless communicationterminal, wherein when the trigger information is included in a triggerframe, the trigger frame comprises a signaling field indicating whetherthe wireless communication terminal is allowed to aggregate one or moreMPDUs requesting an immediate response to generate Aggregate-MACProtocol Data Unit (A-MPDU), determine whether to aggregate one or moreMPDUs requesting an immediate response to generate the A-MPDU based onthe signaling field when the trigger information is included in thetrigger frame, generate the A-MPDU according to the determination whenthe trigger information is included in the trigger frame, and transmitthe trigger-based PPDU including the A-MPDU to the base wirelesscommunication terminal.
 22. The wireless communication terminal of claim21, wherein when the value of the signaling field is a predeterminedvalue, the processor is configured to generate the A-MPDU not to includeone or more MPDUs requesting an immediate response, and when the valueof the signaling field is within a predetermined range, the signalingfield indicates a maximum number of TIDs that is allowed to beaggregated in the A-MPDU when the wireless terminal generates the A-MPDUand the processor is configured to generate the A-MPDU according to themaximum number of TIDs.
 23. The wireless communication terminal of claim22, wherein the wireless communication is allowed to aggregate one ormore MPDUs not requesting an immediate response regardless of themaximum number of TIDs.
 24. The wireless communication terminal of claim23, wherein the one or more MPDUs not requesting an immediate responsecomprises a Quality of Service (QoS) Null frame not requesting an ACKfor the QoS Null frame.
 25. The wireless communication terminal of claim23, wherein the one or more MPDUs not requesting an immediate responsecomprises an Action No Ack frame not requesting an ACK for the Action NoAck frame.
 26. The wireless communication terminal of claim 21, whereinwhen the value of the signaling field is within a predetermined range,the processor is configured to aggregate one or more action framesregardless of a maximum number of TIDs that is allowed to be aggregatedin the A-MPDU when the wireless terminal generates the A-MPDU.
 27. Thewireless communication terminal of claim 21, wherein when the triggerinformation is included in a MAC header, the processor is configured togenerate the A-MPDU not to include one or more MPDUs requesting animmediate response.
 28. The wireless communication terminal of claim 27,wherein when the trigger information is included in the MAC header, theprocessor is configured to aggregate any one of an ACK frame and a BlockACK (BA) frame, with one or more MPDUs not requesting an immediateresponse, without one or more MPDUs requesting an immediate response togenerate the A-MPDU.
 29. The wireless communication terminal of claim28, wherein the one or more MPDUs not requesting an immediate responsecomprises at least one of a QoS Null frame not requesting an ACK for theQoS Null frame and an Action No Ack frame not requesting an ACK for theAction No Ack frame.
 30. A base wireless communication terminalcommunicating wirelessly, the terminal comprising: a transceiver; and aprocessor, wherein the processor is configured to: generate triggerinformation to a plurality of wireless communication terminals using thetransceiver, wherein the trigger information triggers a transmission ofa trigger-based physical layer protocol data unit (PPDU) by the wirelesscommunication terminal and is included in a trigger frame which includea first signaling field, wherein the first signaling field indicateswhether aggregating one or more MPDUs requesting an immediate responseto generate an Aggregate-MAC Protocol Data Unit (A-MPDU) is allowed andindicates a maximum number of TIDs that is allowed to be aggregated inthe A-MPDU when the wireless terminal generates the A-MPDU, when awireless communication terminal corresponding to the first signalingfield is not allowed to aggregate one or more MPDUs requesting animmediate response to generate the A-MPDU, set a value of the firstsignaling field to a predetermined value, transmit the trigger frame,and receive the trigger-based PPDU including the A-MPDU from at leastone of the plurality of wireless communication terminals, wherein one ormore MPDUs requesting an immediate response are aggregated or not, basedon the first signaling field, in the A-MPDU.
 31. The base wirelesscommunication terminal of claim 30, wherein when a wirelesscommunication terminal corresponding to the first signaling field isallowed to aggregate one or more MPDUs requesting an immediate responseto generate the A-MPDU, the processor is configured to set the value ofthe first signaling field according to the maximum number of TIDs. 32.The base wireless communication terminal of claim 31, wherein themaximum number of TIDs indicates a maximum number of TIDs requesting animmediate response that is allowed to be aggregated in the A-MPDU. 33.The base wireless communication terminal of claim 31, wherein one ormore Quality of Service (QoS) null frames not requesting an ACK for theQoS null frames are aggregated in the A-MPDU regardless of the maximumnumber of TIDs.
 34. The base wireless communication terminal of claim31, wherein the trigger frame comprises a second signaling fieldindicating whether channel sensing is required when a wirelesscommunication terminal transmits a response to the trigger informationthrough trigger-based Physical Layer Protocol Data Unit (PPDU), whereinthe processor is configured to set the value of the first signalingfield based on the value of the second signaling field.
 35. The basewireless communication terminal of claim 34, wherein when the secondsignaling field is set to indicate that channel sensing is not requiredwhen the wireless communication terminal transmitting the response tothe trigger information transmits the trigger-based PPDU, the processoris configured to set the value of the first signaling field to thepredetermined value.
 36. The base wireless communication terminal ofclaim 35, wherein the trigger frame comprises a third signaling fieldindicating information on a length of the trigger-based PPDU, whereinthe processor is configured to set the value of the first signalingfield based on a value of the third signaling field.